19．We werethat the Wenchuan earthquake left the whole city in ruins

下面语段划线处标点使用有错误的一项是 （ ）连“坐”字的意义，古代和现代也不完全一样①：古代席地而坐，两膝着席，跟跪差不多，所以《战国策》里说伍子胥“坐行蒲服，乞食于吴市②，”坐行就是膝行③（蒲服即匍匐）④；要按现代的坐的姿势来理解，又是坐着又是走，那是绝对不可能的。（《语言的演变》）

I often help my mom do some cleaning _______ Sundays.

If they had known what was coming next, they_____ their mind.[ ]

May I smoke?-If you______, go and find the smoking area，please!